PFAS (forever chemicals)

Per- and polyfluoroalkyl substances (PFAS) are a class of thousands of synthetic chemicals characterised by extremely stable carbon-fluorine bonds, resulting in environmental persistence and, for long-chain variants such as PFOA and PFOS, serum half-lives in humans of several years. Exposure routes include contaminated drinking water, food packaging, non-stick cookware and occupational contact; PFAS have been detected in blood and tissue globally, including in remote Arctic populations. Epidemiological evidence links PFAS exposure to suppressed antibody responses to vaccines, dyslipidaemia, thyroid hormone disruption, reduced birthweight and increased risk of kidney and testicular cancers, with mechanistic pathways involving PPAR-alpha activation and nuclear receptor interference. In April 2024 the US EPA finalised the National Primary Drinking Water Regulation, setting enforceable maximum contaminant levels for PFOA and PFOS at 4 parts per trillion in drinking water; in May 2025 EPA retained the 4 ppt MCLs for PFOA and PFOS but announced its intent to rescind the MCLs for PFHxS, PFNA, GenX/HFPO-DA and the Hazard Index mixture limit (which covers PFHxS, GenX, PFNA and PFBS), and extended PFOA/PFOS compliance deadlines by two years; as of May 2026 the rescission proposal remains in rulemaking; the EU is pursuing a parallel restriction under REACH covering entire PFAS groups.